Dietary caloric restriction (CR) is the most effective known strategy for lifespan prolongation and cancer prevention in laboratory animals. Our project's aim is to explore several possible mechanisms responsible for these effects. The First Hypothesis relates to nutritional parameters: we suggest that the usual regimen of CR, which consists of intermittent feeding/starvation, may contribute to some of the reported immunologic and endocrine effects, though certainly not to the lifespan extension. Any differences due chiefly to the feeding/starvation schedule itself may not be fundamental to CR effects on aging, and should largely be eliminated from consideration in the search for mechanisms. We will investigate this aspect of CR by comparing selected immunologic and endocrine parameters in mice fed small amounts 6 x/day with an automated feeder to those fed by the traditional intermittent schedule. Second Hypothesis: we suggest that many immunosenescence phenomena correctable by CR are not primarily T and B cell defects, but secondary to age related macrophage (MO) dysfunction, i.e. that the MO is primary in much of immunosenescence. The effect of age and CR will be assessed for MO antigen presentation of influenza and hen egg lysozyme, using T cell hybridomas as well as memory T cells in the assays. Extending this, we will determine whether correcting MO dysfunction by non-CR methods will ameliorate those aspects of immunosenescence which are corrected by CR. Determining the effects of age and CR in relation to several MO cytokines, 1L1, 1L6, TNF and TGF Beta, will further enlarge these perspectives. For TNF, in vivo production and response to the cytokine will be measured in several organs following BCG inoculation. Finally, as a Third Hypothesis: the role of gene expression and of DNA binding proteins as regulatory targets for CR will be explored in a subcontract project. This hypothesis is based on previous collaborative CR data showing a paradoxical change in glucose-regulated protein (GRP gene expression. The study may provide the first insight into a genetic process modifiable by CR.